Speed sensitive locking devices are used in many applications, for example, safety brakes for hoist lines, seat belt restraints, and safety catches for doors. Some conventionally known devices employ the action of centrifugal force on a governor or spring-biased triggering member, e.g. on a wheel for hoist lines. Another type of device, such as shown in U.S. Pat. No. 2,979,282 issued on Apr. 11, 1961 to Barecki, uses a pivotable catch lever to arrest a ratchet wheel when its rotational speed is too high. Yet another known device, shown in U.S. Pat. No. 3,504,556 issued on Apr. 7, 1970 to Mills, uses a wavy crested rack and a follower roller on the end of a lever which triggers a locking device.
Conventionally known devices have the disadvantage that they generally require complex mechanisms which are difficult to operate with a high degree of reliability. Many are required to be assembled within the housing of a device, such as an automatic reel or brake, and therefore are not suitable to be retrofitted to existing uses which were not originally provided with a speed sensitive lock. Others known safety locks are employed around a rotating reel or wheel, and cannot be used to arrest a member moving in a linear direction.
The inventor has identified many existing devices and environments which may not have been originally provided with a speed sensitive lock. For example, the throttle levers on boats and other vehicles are generally mounted from the side of a housing and are operated in one or the other direction to accelerate and decelerate an engine. Throwing the lever in one direction too quickly may result in damage to the engine or stripping of the gears. Similarly, brakes and other control levers for machinery which are pulled to a stop position against a spring force may be accidentally dislodged from the stop position and flung to the release position at a high speed.
Accordingly, it is a principal object of the invention to provide a speed sensitive safety lock which has a simple and reliably operated structure, and which can be easily retrofitted to a wide variety of existing devices and operating environments. In particular, it is desired to provide a lock which can be readily mounted onto the side of an existing housing for a moving control lever or other member, or which can be easily installed during the original assembly of a wide variety of devices. It is a further object of the invention to provide a speed sensitive lock which has a small number of moving parts, preferrably only one, and which nevertheless can reliably arrest and hold the moving member.